Configure the default content workflow suitable for your site. Out of the box, Drupal modules are set to promote to the front page. While this is desirable in many instances, it is not something you always want.
Go to Administer > Content Management > Content types
Click on the configure for the node type in question and change the default workflow options to something suitable for your site.
If you add or enable modules such as CCK that create additional node types, you will need to revisit these settings. Remember that.